Opinion on wearing masks against COVID-19

Fighting the pandemic on two fronts: against the virus, and against pseudoscience

Writer: Bence Kover
Editor: Natalia Sanchez
Artist: Sophie Maho Chan

The anti-vaccination movement found its little brother in the form of ‘anti-maskers’, and now stronger than ever, together they are posing a significant threat to public health, evidence-based medicine, and science itself. Ironically, wearing masks is the least economically detrimental non-pharmaceutical intervention, yet it still became the most controversial policy during the coronavirus pandemic. What originally represented a time-tested method for controlling pandemics became politicised; masks are mere symbols of compliance with government guidelines nowadays. However, public health should primarily be a scientific and medical issue, and if we want to act responsibly, we need to rely on scientific evidence when choosing sides in the ‘mask debate’.

While SARS-CoV-2, the virus causing COVID-19, can be transmitted via physical contact, it is primarily spread by liquid droplets or aerosols during breathing, talking or coughing. The role of masks is not only to inhibit the inhalation of these viral particles, but also to prevent their emission by an infected individual in the first place. In fact, research shows that while masks are mainly effective in source control, when worn by both the spreader and the receiver, the protective effect is greater. This means that their purpose is not just the protection of the wearer, but mainly the altruistic protection of the community. Historically masks have been shown to be effective against various respiratory viruses, including SARS, MERS, and types of influenza. However, masks are just one of many non-pharmaceutical interventions, including social distancing and frequent hand sanitising, and their success partly relies on public compliance with other public health guidelines

Masks are generally grouped into three categories in the media and in the scientific literature, namely N95 respirators, surgical masks, and cloth masks. N95 respirators, by definition, filter out 95% of particles that are above 300 nm in diameter, while surgical masks are slightly less effective. There is established literature on the efficacy of these masks, and also a long history of medical usage. Nonetheless, they have two main problems; they are single-use, so create large amounts of waste, and their supply is finite. Therefore, N95s and surgical masks were mainly recommended for healthcare workers, and the general public has been advised to use cloth masks instead.

Government agencies around the world have mostly provided flawed information regarding cloth mask design for the public. Research shows that using only a single layer of cotton or a loosely-woven material (like a scarf) has no effect with regards to filtering airborne particles. Furthermore, reusing cloth masks, or not properly cleaning them, can plausibly increase the chance of infection, which can be exacerbated by their moisture retention. One article raised concerns about cloth masks shedding microscopic particles, which could potentially aerosolise viruses and cause infections. Currently, there isn’t sufficient data to support this hypothesis, and as always, further research is necessary. 

That said, evidence shows that a design with proper fit, using multiple layers of hybrid cloth, usually tightly-woven cotton with flannel, chiffon or silk, can replicate the filtration efficiency of surgical masks. This is thought to be because the cotton layer provides a mechanical barrier, while the flannel/ chiffon layer acts as an electrostatic shield. Other slightly grotesque solutions include wrapping a nylon stocking around the facemask, or stuffing paper towels between the cloth layers. Irrespective of the exact design, having multiple such cloth masks at hand, and washing them after a single day of use, which can just mean putting them in the laundry, can be a sustainable and safe solution.

Furthermore, mathematical modelling found that considerable public compliance with mask-wearing policy can significantly flatten the curve, even if masks were only moderately effective. Masks are also a useful precautionary measure when it comes to the high number of asymptomatic and presymptomatic individuals, reminding us that it is not enough if only symptomatic people wear masks. Observational studies have shown that mask usage did indeed ‘flatten the curve’ in some areas, such as Hong Kong, which had lower case numbers than countries with similar population densities and healthcare systems.

While masks are clearly effective when used properly and in conjunction with other non-pharmaceutical measures, there is an emerging fear that they can induce feelings of overconfidence and reduce compliance with social distancing and handwashing guidelines. Unfortunately, there isn’t any meaningful research on this topic, but being mindful of these caveats is definitely helpful.

Looking at the evidence, we can conclude that wearing face masks is an effective non-pharmaceutical measure against SARS-CoV-2, however the wearer should be aware of the possible design flaws and psychological caveats. On these grounds, we can dismiss the pseudoscientific claims of the anti-mask movement and advise the general public to wear cloth masks, while N95 respirators and surgical masks should be reserved for healthcare workers and the elderly. With all the uncertainty introduced into our lives by COVID-19, there are very few things we can be confident about, but the protective effect of face masks is definitely one of them.

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